Figured it out: if in TXT input options either
auto or
heuristic formatting style has been selected, the text is smartened regardless of the setting in Look & Feel.
I'd rate this as a minor bug, since the user expectation would be that the checkbox on Look & Feel is what governs this function - now the preference gets silently ignored depending on TXT input formatting style.
This is the block in txt_input.py
Code:
if options.formatting_type == 'heuristic':
setattr(options, 'enable_heuristics', True)
setattr(options, 'unwrap_lines', False)
setattr(options, 'smarten_punctuation', True)
meaning that whenever the setting is
heuristic smarten_punctuation is always true, and
auto apparently always runs as heuristic.